Sidney



Reissue-d r 29,

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or cnrca eo. vlearners sum-roe ru'rn' 151mm Original sofa-teaser, emu member mo, Serial 10. mm, m Tehran-7 11.1.9.

I Application for reissue fled Jane 8, 1881. Serialll'o. 548,887;

vMy invention has to do with separators for use in electric storage batteries and electrolytic cellsnofvarious sorts.

One object of my invention, generally stated, is to provide an improved separator which is highly permeable, creates but'little loss is replaced by the conversion ofadditional electrode material to the active form.

. Ultimately there is insufiicient material left .to provide the. necessaryIcapacity and the plate isworn out. Ifthis loosened active as materialcanbe held in contact" with the electrode it continues to function normally and greatly increases the useful electrode life.

The separators heretofore most commonly used have been made of wood, or wood in so combination with other materials, as for ex ample, rubber, felted glass wool, etcl. Wood separators have several serious disadvantages. When out into sheets sufiiciently thin to ofier minimum resistance, wood is extremely fragile and possesses relatively" low mechanical stren 7 Another objection to the use ofjwood separators is that, under'normal operating am ditions in a battery, certain substances are extracted from the wood which have a most deleterious efiect on the performance and life of the battery (of, Vinal and Schramm, Journal Amer-Inst. of Elec. Eng, p. 128, Feb. 1925). Probably the greatest single objection to wood separators, however, is their necessarily short life. Wood, being cssentially cellulose, is gradually deh drated' a-reby the sulphuric acid electrolyte. sult,-the separator shrinks and splits, perniitting passage of'the active material and "with in, the past, but they-have either consequently short-circuiting. Furthermore, the dehydrated and charred wood, being largely carbon, is itself 'conducting and so further increases the losses of internal energy. The average life of a wood separator late .m service is from one to two years. en broken down it must be replaced. The most 4 common cause for rebuilding batteries is the necessity for replacing the woodseparators; Without the requirement for this expensive replacement, a battery under ordinary condi- Y tions could remain in continuous service for a period much'longer than the life of the wood separator components. 1

Se arators made of materialsother than w have been proposed and experimented sessed one or more of'the .above descn objectionable features or have been too expensive to be used commercially.

I have discovered that a separator having the desirable characteristics outlined above,

and free from the objections inherent in wood separators, may be produced by using as the body of such separator, particles on sllicagel from which the water has been largely or entirely removed, the dehydration being car- 'riedto such a point that the dried material has assumed substantially its ultimate physical structure, possesses a vitreous luster, has great mechanical strength, and will not revert to a mushy or gelatinous form when treated with water or other liquid.

I am aware that others have'contemplated the employment of silica gel in connection with the production of separators, but not in the form and manner in which I make use of the same. The permeability of silica gel to electrolytic ions is well known, but those to whom I have referred as having contemplated its employment in separators have proposed to make use of it, not in its hardrig- 1d and non-revertible form as the principal material of the body of the separator supplyingtthe necessary rigidity thereto, but m its so and moist gelatinous form as filler material extending across andobstructing rela-" tively large 0 enings in a porous diaphragm made of a di erent more" rigid material. 7

In this specification and lo the appended claims, by silica gel I mean theliard, rigid,

substantially dry material, definitely dehyx The following example is presented herein merely for the purpose of exemplification.

It will be appreciated that both the-formula and the procedure set forth in such example are susceptible of modification without constituting a departure from the invention as defined in the appended claims."

The silica gel may be prepared by any suitable method, as for example by the method disclosed in my copending application Serial No. 46,890, filed July 29, 1925, (now Patent No. 1,755,496, granted April 22,1930), or by the method disclosed in Patrick Patent No. 1,297,724., or by the method involving the acid treatment of silicates disclosed inmy copending application Serial No. 46,889 filed July 29, 1925. The hard form of silica gel produced by the process disclosed in my copending application, and when dried to constant weight at about (3., usually contains about 12 of water and has an apparent density of about 30 lbs. per cubic foot. Thisdry material will absorb 90 to 100 per cent of its own weight ofwater. In spite of this tremendous porosity, the particles of dry material are glassy and almost perfectly transparent. xamination-with a powerful microscope fails to reveal any porous structure, so thatthe pores are evident-1y submicroscopic, as is characteristic of such materials.

The rubber cement may be any one of the common rubber cements now on the market, such as Goodrich No. 4, which is essentially a solution of rubber in benzol and containing about 7% by-weight of rubber.

I take about 1000 grams of the silica gel, preferably between 40 and 100 mesh screen size and mix it with about 1360 grams of the rub r cement in any convenient way, as for example by the employment of a kneading machine,

The size of silica gel particlesem loyed may be made to vary widely, and will epend largely on the particular requirements in each case. For example, in certain cases where maximum elasticity is not essential, I

use silica gel particles ranging in size chiefly from 10 to 20. mesh. .In this case, I prefer to use considerably less rubber cement than in the previous example, and to harden the rubber slightly by means of sulphur chloride or some other .vulcanizing agent.. Ob-

'rator has solidified.

viously, the greater the proportion of silica gel in the separator plate, and the less the proportion of binder, the greater will be the porosity of the plate, and the more direct and the electrolyte.

' The mixing operation is preferably performed in a closed container in orderto avoid premature evaporation of thesolvent. After uniformv mixing has been obtained, the resulting plastic mass is pressed, extruded, molded orotherwise formed into the desired shape. This may be a flat, ribbed or grooved plate, or any other form well known in the art.

The plate is then allowed to dry. The drying operation'may take place at room temperature, but is preferably carried on at a temperature somewhat higher than room tem peraturein order to expedite evaporation of the solvent. If desired, the solvent may be recovered by any of the processes well known to chemical engineering practice.

A separator plate constructed in accordance with my invention is light in weight, highly permeable, resilient and yielding, and has ample. mechanical strength for the purpose for Y which intended. If greater rigidity is desired, the rubber binder may be hardened to. i

almost any degree by proper compounding or other process known to rubber technology, the method of incorporation of the binder with the gel, and the subsequent treatment, being determined by the requirements of the particular process employed.

When the separator is first prepared, a large part of the minute pores may be filled with air, in. which condition the separator might offer considerable resistance to the passage of the ions of the electrolyte. In order to remove the air, the separator may be subjected to a vacuum treatment while in contact I with a liquid, which liquid may conveniently be the electrolytein which it is to be used. The air may be removed after the separator has been placed in the cell of a battery by lacing a vacuum on the cell. When the air is removed from the separator before the assemblage of the battery, the air-exhausted I separator, filled with liquid, is preferably packed in awater-tight wrapper or container and is kept in that condition until inserted in the cell of the battery.

The high porosity of a separator constructed in accordance with my invention may be made to result either entirely from the permeability of the silicagel particles, or inv I part from minute voids between the particles of the silica gel not occupied by the rubber or other binding material.

To provide even more porosity, I may include with the base and binder one or more soluble or volatile compounds, such as sodium sulphate, ammonium sulphate, etc. which may be dissolved out or volatilized after the sepa- Before mixing the particles of silica gel and binding material, I may first wet the silica gel particles with water or other liquid in order to fill the pores and so prevent entrance of the binding material.

I have also discovered that I can roduce a satisfactory separator by using drie permeable particles of other gel-like materials such as zeolites, silicates, or the like, in lace of the silica gel, and by using instead 0 rubber other inert binders such as celluloid, shellac,

.' described in the foregoing, additional porosity is obtained by reason of the minute voids resulting from the solution by the electrolytic acid of the metallic oxides of the silicates.

m For example, if glauconite, which in its natuwill be found in the chemical and allied arts ral state is essentially a complex hydrated silicate of potassium and iron, is treated with sulphuric acid, the potassium and iron oxides are dissolved out in the form of potasg5 sium and iron'sulphates, respectively, leaving a highly porous and rigid skeleton of substan tially pure silica; or if [sodiumv aluminum silicate material, such as that prepared by the process of m Patent No. 1,515,007, is

treated with sulp uric acid, the sodium and aluminum oxides are removed, leavi-n an extremely porous gel-like siliceous s eleton. Processes of preparing such highly porous siliceous products from the raw materials referred to are disclosed in detail in m copending application, Serial No. 46,889, ed July 29, 1925. The treatment with acid is preferably employed outside the battery, in order to avoid the possibility of deleterious effect on the battery of the reaction productse. g. iron sulphate, aluminum sulphate, etc.

While the present invention, for the purposes of this application, is concerned primarily with the use of the new composition of matter disclosed for the purposes of battery separators, it is obvious that other uses for this highly permeable and inert product. I' claim l 1. A separator consisting of hard highly orous particles of a siliceous gel material lield in place by an inert binder. l J

2. A separator consistin of particles of dried silica gel held in p ace by an inert binder.

3. A separator consistin dried silica gel held in p ace by an inert flexible binder.

4. A separator consisting of particles of dried silica gel held in place by rubber cement.

5. A separa or composed primarily of hard silica gel particles held together by an inert binder.

6. A separator composed primarily of hard of particles of silica gel particles held together by an inert binder, said separator having voids in the binder between the articles.

7. A se arator p ate containing particles of hard si ica gel.

8. A separator plate consisting of silica gel and an inert binder.

9. The process of producing a separator plate which consists in mixing particles of a hard siliceous gel material with a binder and forming the mixture into the shape of separator desired.

10. The process of producing a separator plate which consists in mixing particles of a hard siliceous gel material with a binder in solution, formin the mixture into the shape of separator esired, and drying the separator to remove the solvent.

11. The method of producing a se arator plate which consists n mixing dri silica gel particles with a rubber cement, forming the mixture into-the shape of separator desired, and drying the separator to remove the solvent. I

12. A new composition of matter, comprising dried particlesof silica gel mixed with a binder.

13. An article of manufacture, com rising dried gel particles having substantial y continuous porosity, mixed with a binder.

14. A permeable composition of matter comprising dried gel particles having substantially continuous porosity, held in jux-- taposition by rubber. I

15. A permeable separating material, comprising ri d gel-like particles of an inert nature an having substantially continuous pores of minute size, held in 1uxtaposition y an inert binder.

'16. An article of manufacture, comprisi dried particles of a gel-like material mixe, with a binder.

17. A permeable composition of matter comprisin dried hard particles of a gel-like material eld in juxtaposition by rubber, said particles having substantially continuous pores of minute size.

18. A'permeable composition of matter, comprising dried articles having a continuous porosity simi ar to that of dried silica gel, mixed with a binder.

19. A permeable diaphragm for use in connection with liquids, comprising rigid particles of a gel-like material, mixed with an inert binder, said particles havin a sub stantially continuous porosity and ein inert to the liquid in connection with w 'ch said diaphragm is used.

In testimony whereof I have hereunto subscribed Ali 1f name.

ABR AM SIDNEY BEHRMAN. 

